C-Jun N-Terminal Kinase Mediates Calcitonin Gene-Related Peptide Expression in Rat Trigeminal Ganglion in Vitro

Objective: Calcitonin gene-related peptide (CGRP) plays a prominent role in migraine pathophysiology. However, the underlying molecular mechanisms that are responsible for regulating CGRP expression are not fully understood. Using an in-vitro model of organ culture of rat trigeminal ganglion (TG), the present study aims to investigate the role of c-Jun N-terminal kinase (JNK) in regulation of CGRP. Methods: The TG was isolated from Sprague-Dawley (SD) rats and then organ cultured in presence of inflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) (50 mu g/L) or interleukin-1 beta (IL-1 beta) (25 mu g/L) with and without a specific JNK inhibitor SP600125 (10(-5M)) or an anti-migraine drug sumatriptan (0.5g/L) for 24h. Real-time polymerase chain reaction (RT-PCR) and Western blotting were used to evaluate the CGRP-mRNA expression and phosphorylated JNK (pJNK) protein in rat TG after the organ culture. Results and Conclusions: The JNK inhibitor significantly reduced the organ culture and cytokines-induced up-regulation of CGRP-mRNA expression compared with control (P<0.05), indicating that a transcriptional mechanism was involved. Interestingly, the anti-migraine drug sumatriptan had similar effect. Western blotting showed that the cytokines significantly increased pJNK protein level, while this increase could decrease by sumatriptan and SP600125 (P<0.05), demonstrating that JNK mediated the up-regulation of CGRP expression induced by the cytokines. This may suggest a novel pharmacotherapeutical target for migraine treatment.